import ST

fact n = setST xP 1 `bindST` \ _ ->
         setST yP n `bindST` \ _ ->
         (let _while = getST yP `bindST` \ y ->              
                       if y > 0 then
                            getST xP         `bindST` \ x ->
                            getST yP         `bindST` \ y ->
                            setST xP (x*y)   `bindST` \ _ ->
                            getST yP         `bindST` \ y ->
                            setST yP (y-1)   `bindST` \ _ ->
                            _while
                         else unitST ()
            in _while)   `bindST` \ _ -> 
         getST xP

main = print (fst (fact 9 (0, 0)))